A conventional locking device for a tool box is integrally connected to the base portion 1 of the tool box by way of plastic mold injection or plastic blowing so that there will have a surplus portion 12 attached to the periphery of the base portion and another surplus portion 13 attached between the locking member 11 and the engaging portion 111 of the locking member 11. In order to remove the surplus portions 12, 13, the manufacturers have to take time to cut the surplus portions 12, 13 by blades. However, this removing of the surplus portions 12, 13 is required certain skill so that a high price of the tool box is incurred. Furthermore, the operators cannot cut the surplus portions 12, 13 evenly because they use the blades with their hands so that the material of the tool box could be removed too much. In addition, when transporting the tool boxes, it is impossible to overlap the tool boxes because there has no suitable connecting device for securely connecting the overlapped tool boxes. Therefore, the manufacturers and the users are forced to carry two or more than two tool boxes separately.
The present invention intends to provide a locking device for a tool box wherein the locking device can connect two overlapped tool boxes together. The locking device of the present invention provides a new function so as to mitigate and/or obviate the shortcomings of the conventional locking device of the tool box.